A maskless lithography imaging simulation using digital micromirror device (DMD) was investigated. The DMD acts as a reflective spatial light modulator. The micro-mirrors on DMD can be instructed by the computer to tilt them ±12° off their normal position which produces a mask pattern, and then the mask pattern can be carried onto the surface of wafer by the imaging system. Because the imaging of the maskless lithography is a complex process, it is necessary to simulate and analyze its practical process. In this paper, we present a partial coherent imaging model of maskless lithography considering the practical projection characterization of DMD. With the model, it is convenient to simulate the lithography of arbitrarily shaped microstructure using DMD. Through calculation, the spatial image in maskless lithography process based on gray scale photolithography with DMD real-time masks was obtained.
Experimental and theoretical analysis indicates that many nonlinear factors existing in the exposure process of thick resist can remarkably affect the PAC concentration distribution in the resist. So the effects should be fully considered in the exposure model of thick resist, and exposure parameters should not be treated as constants because there exists certain relationship between the parameters and resist thickness. In this paper, an enhanced Dill model for the exposure process of thick resist is presented, and the experimental setup for measuring exposure parameters of thick resist is developed. We measure the intensity transmittance curve of thick resist AZ4562 under different processing conditions, and extract the corresponding exposure parameters based on the experiment results and the calculations from the beam propagation matrix of the resist films. With these modified modeling parameters and enhanced Dill model, simulation of thick-resist exposure process can be effectively developed in the future.
In this paper, we present a new technique for adjusting and controlling the playback wavelength of Lippmann holograms recorded in methylene-blue sensitized dichromated gelatin (MBDCG). During the preparation of photosensitive layer, a water-soluble organic reagent, acrylamide is added homogeneously into our optimum MBDCG recipe as preswelling reagent. It will be dissolved completely into water during the postprocessing procedure and result in the uniform shrink of the fringe planes of reflection hologram, which will makes the playback wavelength shift relatively to shorter wavelength. This method can be applied to adjust the playback wavelength of reflection hologram quantitatively by changing the concentration ofpreswelling reagent.